What cost police protection?

This photograph was snapped outside No 10 Downing Street on Saturday, 3rd December 2005 during a peaceful protest against the Bush/Blair
betrayal on climate control. The column halted on the far side of Whitehall whilst two representatives handed in a petition.

There was no trouble and the protestors were remarkably well-behaved yet this enormous number of uniformed officers blockaded the entrance to
Downing Street. We have to accept that precautions must be taken during these troubled times but do we actually need this many officers,
particularly as the PM normally spends weekends at his Chequers country retreat?